Conscience

Man is distinguished from the rest of creation by his intelligence and his freedom. He matures in his manhood by growing in wisdom and by gaining a more prudent and effective command of his own moral activity. Character and maturity are therefore measured by the clarity and discretion of our moral conscience. Conscience is the summary of the whole man, although a man is much more than an animated conscience. Conscience is the indication of hidden things, of imperceptible acts and tendencies that are much more important than itself. It is the mirror of man’s depths. The reality of a person is a deep and hidden thing, buried not only in the invisible recesses of man’s own metaphysical secrecy but in the secrecy of God Himself.

Conscience is the face of the soul. Its changing expressions manifest more precisely the moral action of the soul than the changes of man’s countenance manifest the emotions within him. Even the outward face of man is only a reflection of his conscience. True, only a very little of what is in a man’s soul ever shines out in his face: but the little that is there is enough to speak eloquently of the conscience within.
---Thomas Merton "No Man Is An Island"